Method for manufacturing shaft seals



Aug. 30, 1960 e. L. CORS! 2,950,506

METHOD FOR MANUFACTURING SHAFT SEALS Original Filed April 8, 1955 2Sheets-Sheet 1 FIG. 4

Aug. 30, 1960 cs. L. CORSI 2,950,506

METHOD FOR MANUFACTURING SHAFT SEALS Original Filed April 8, 1955 2Sheets-Sheet 2 FIG. 5

FIG.7

Patented Aug. 30, 1960 METHOD FOR MANUFACTURING SHAFT SEALS George L.Corsi, Detroit, Mich, assignr, by mesne assignments, toFederal-Mognl-Bower Bearings, Inc., Detroit, Mich., a corporation ofMichigan Original application Apr. 8, 1955, Ser. No. 500,161, now PatentNo. 2,837,359, dated June 3, 1958. Divided and this application July 26,1957, Ser. No. 676,465

4 Claims. (CI. 18-59) This invention relates to a method formanufacturing shaft seals and more particularly to an improved method ofmaking a unique seal construction featuring simplicity, ruggedness,flexibility in its mode of application, ease of installation yet greatretentive power, low cost, and others. This application is a division ofco-pending application Serial No. 500,161, filed April 8, 1955, nowPatent No. 2,837,359, which relates to the product aspect of theinvention.

One of the prime objects of the invention is the provision of a sealdesign and mode of making the same wherein the reinforcing ring for theresilient sealing element is substantially enclosed except for a narrowexposed band arranged to provide a metal-to-metal con-' tact with thesupporting structure for the seal at its point of use.

Another object is the provision of a method for making shaft sealshaving a reinforcing ring embedded within a molded sealing element andhaving a rim adapted to be exposed when the outer axial edge of the sealis subjected to a finishing and sizing operation.

Yet another object is the provision of a method for making metalreinforced shaft seals of elastomeric material having a radially exposedband of metal located between coverings of elastomer bonded to itsopposite faces and acting as sealing gaskets as well as protectivecoverings for the metal irrespective of which way the seal is installedinto a bore.

A further object is the provision of unique means for supporting areinforcing ring centrally of a mold cavity while surrounding the samewith semi-plastic elastomeric prep material under high pressure.

Another object is the provision of a method for molding a shaft sealhaving a metal core ring encased between layers of resilient coveringmaterial, the rim edges of which cooperate with the exposed edge of thecore ring to provide a gasketed metal-to-metal anchor for the seal whenmounted in a housing.

Numerous other objects and advantages of the invention will becomeapparent from the following detailed specification covering illustrativeembodiments of the invention taken in connection with the accompanyingdrawings, wherein:

Figure 1 is a fragmentary isometric view in section through a preferredembodiment of the seal before being trimmed and sized;

Figure 2 is a fragmentary sectional view through the finished seal asmounted on a shaft according to one mode of use;

Figure 3 is a view similar to Figure 2 but showing the same mounted on ashaft according to a second mode of use;

Figure 4 is an end elevational view showing one man- Figure 6 is a viewsimilar to Figure 1 of a trimmed seal; and

Figure 7 is a fragmentary view of the male die ring used in molding theseal construction.

Referring to the drawings, it will be seen that my lubricant sealingring comprises but two components, namely, a cupped rigid reinforcingring 10 and a covering of mol able resilient synthetic elastomer 11. Thereinforcing ring is preferably formed from sheet steel stock of fairlyheavy gauge. As shown in the preferred embodiment, the ring isogee-shaped in cross-section and includes a radial inner n'm 12, arelatively narrow radially disposed outer rim 13 lying in a plane ofisetaxially from rim 12 and connected to it by a frusto-conical web 14.Manifestly, the shape and disposition of connecting web 14 provides ahigh-strength reinforcement for the inner and outer rims 12 and 13.

As made clear by Figure 2, core ring 10 is substantially fully embeddedin the synthetic covering of elastomer selected from any of a number ofsynthetic rubber compounds well-known to those skilled in this art andhaving high resistance to attack by lubricating mediums. Thus, both theinner and outer surfaces, and particularly the outer rim areas of thering, are covered with thick layers of the elastomer. Integral with theinner rim of these covering layers is a sleeve-like shaft engaging lip15 having a thin-walled flex section 16 bonded to the inner rim 12 ofthe ring. The opposite or free end of the sealing web 15 is providedwith a sharp lip edge 17 having a diameter slightly less than that ofthe shaft 18 on which it is to seat in use. Encircling the exterior oflip 17 is a spring seating groove 19 for a garter spring 29.

This is an appropriate point to note that the layer of resilientcovering material for ring it} may be comparatively thin except in thearea forming the outer mounting rim of the seal and generally indicatedat 21 and 22. The layers at these points are very thick to form a widecylindrical surface engageable with the bore sidewall in the place ofuse. These thick layers of resilient material provide sealing gaskets aswell as means cooperating with the exposed edge of rim 13 for holdingthe seal rigidly anchored to its housing.

Another interesting feature of the invention is the simple but highlyefiicient mode devised to hold the reinforcing ring centered in amolding cavity while the elastomeric material is forced to flow underhigh pressure to all parts of the cavity. Referring to Figure 5, it willbe seen that the mold comprises a bed plate 25 to the center of which isattached an upright pilot pin 26 to assure proper registry with anopening 28 in the upper vertically movable closing plate 27. The tworemaining principal elements of the mold include a male die ring 29 anda spacer ring 30. The mating surfaces of this mold are, of course,finished to very high tolerances so that when the parts are closed themating surfaces will prevent the escape of stock despite the very highpressures applied against it by a conventional hydraulic press, notshown. The surfaces which cooperate to form the cavity generallyindicated at C and suitable for molding the seal are shown in Figures5-7.

The means for holding ring 10 centered in cavity C comprises anupstanding frusto-conical shaped spider 31 at the inner periphery ofmold ring 29. The radial face of spider 31 is provided with low-heightlarge area bosses 32 separated from one another by stock flow passages33. Bosses 32 provide a multiplicity of extremely strong supports forinner rim 12 of the reinforcing ring. Bosses 32 also cooperate to formradial flow-passages 33 inter-connecting the opposite sides of spider 31and through which the semi-fluid uncured elastomer (known to thoseskilled in this art as prep) can flow quickly and in large volume duringthe molding operation. Note that the edge of rim 13 of the ring layer ofrubber will inevitably cover edge of rim 13 during themolding-operation. However, this is not objectionable since it is asimple matter, according to this invention, to remove this layer duringthe sizing and flash removal operation.

Another important feature of the invention is that the connecting web 14is of frusto-conical shape; This enables the ridges of the fluted outersurface 31 of the mold spider to directly contact the inner side wall ofthe web 14. Likewise, the exposed upper ends of the bosses 32 of thedie, seat against and support the inner surface of the flange 12 of thering.

While the web 14 of the'ring has been shown as flaring outwardly fromthe inner flange 12,'and the fluted surface '31 of the mold spider hasbeen shown as flaring in the same degree, it will be obvious that theweb 14 and the fluted portion of the spider may be of cylindricalformation. This alternate shape will facilitate the manufacture of themold and assure more accurate centering of the ring 10 in the moldcavity. It will likewise be understood that the many advantages flowingfrom this method of centering a core ring in a mold cavity may beenjoyed whether or not the seal has an exposed outer radial flangesimilar to the flange 13.

The important consideration is that'the mold spider 31 be provided witha plurality of bosses 32 and intervening depressions 33, or with closelyspaced, alternately arranged ridgesand valleys to hold the metal coreaccurately centered in the cavity while permitting free flow anddistribution of prep material to all parts of the cavity without dangerof deforming or displacing the ring.

The molding operation is carried on in the following simple andexpeditious manner. It will, of course, be understood that the moldshown in Figure is placed between the upper and lower platens of ahydraulic press of the usual type employed for such operations and willhave well-known provision for heating the mold to cure the elastomer.Mold ring 25 'is supported on the lower platen while the upper platenbears against the upper or core ring 27. While the mold parts are inopen position,

7 ring 1% suitably coated with a bonding agent is dropped into the moldwith its inner rim 12 directly supported by bosses 32 of spider 31. Notethat the radial centering of the ring is facilitated by the slightlyflaring inner sidewalls of spacer ring 30. After a thick ring of uncuredprep has been placed on top of ring 16, and the assembly of the mold hasbeen completed, the upper platen is energized to close the mold. As thistakes place, the prep is forced to fill every part of the cavity as theair bleeds out through the closely fitting surfaces between the moldrings. Note that the stock distributed to the lower surface of thereinforcing ring must pass through the radial passages 33 between bosses32 of the spider. The extremely high hydraulic pressures required toaccomplish this flow at high speed are prevented from shiftingreinforcing ring in the cavity because the initial supply of prep islocated above the ring. The ring cannot move downwardly because of thefirm support provided by bosses 32. And, of course, the ring cannotshift laterally because it is held accurately centered by the engagementof rim 13 with sidewall of spacer ring 30. Nevertheless, a thin flash ofstock does normally form between the bosses and opposed surface of thering.

{Following curing of the elastomer by heat and pressure, semi-finishedseal is removed from the mold. It then has the appearance depicted inFigure 1 due to the presence of three thin webs of flashing 35, 36, and37, as Wellies a thick ring of flashing 38 generally known in the art asthe hat; Flashings 35 and 36 may be removed by trimming the corners on abevel as illustrated in Figure 7. Preferably, however, these fiashingsare removed simul taneously with and as an incident to the sizing andfinishing operation as will be described presently. Flashing 37 and hat38 are removed during the trimming of the seal lip 17 along the conicalsurface suggested by dotted line 39 in Figure 1. This lip trimmingoperation is carried out with the aid of a trimming machine inaccordance with conventional'practice.

The remaining operation is that of accurately sizing the seal and thiscan be speedily and economically performed to a high degree of accuracyin a c enterless grinder of the general type illustrated in. Figure 4.The seals to be finished are indicated at 40 and are arrangedside-by-side as they are gradually fed axially along guide rail 41between a back-up wheel 43 and an abrading or grinding wheel 44. Bothwheels rotate toward the seal 40 but at different speeds. with theresult that the seal rotates as its exterior surface is finished. As theseals pass through the grinder, both the synthetic material and the edgeof outer rim 13 are accurately finished to the same pre-determineddiameter. In other words, the finished edge of the reinforcing ring liesflush with the cylindrical surface of thick elastomer layers 21 and 22to either side thereof. Moreover, flashing rings 35 and 36 are easilyand efficiently removed as the seals progress through the grindingmachine. When the seal emerges from grinder 42, it is ready for garterspring 20 and installation in the housing bore of a shaft. 7

One of two alternate modes of installation is illustrated in Figure 2wherein a shaft 18 is supported by a ball bearing 48 in a housing wall49 having an oil seal seating bore 50. The sidewall of bore 50 isfinished to a diameter slightly smaller than that of seal 40.Consequently, seal 40 must be pressed into the bore under-pressure.Since there is no direct backing for the thick layer 22 of elastometer,it is a simple matter to start the seal into the bore with the aid ofthe chamfered edges of both theelastomer 21 and 22 bonded to theopposite surfaces of the core ring are held firmly pressed against the'bore wall to assure a fluid tight joint without placing gasketing material under any substantial radial pressure. Consequently, there is notendency for the gasketing material to cold-flow out of sealing contactwith'the bore wall. A thin narrow band of gasketing material immediatelyto the left of metal flange 13 is directly backed up by connecting web14 of the ring. Accordingly, it is under somewhat greater radialpressure than the remaining portions of the gasket and provideslife-long assurance of a fluid seal with the bore wall.

Figure 3 is illustrative of the adaptability of the present design formounting in a bore with either face of the seal foremost. The face ofthe seal which first enters the bore is commonly referred to in theart'as the toe of the seal, while the trailing face is known as theheel. Thus, in the Figure 2 mounting, the thickened gasket portion 22acts as the toe and is pressed against the shoulder at the bottom ofbore 50. In the Figure 3 mode of use, gasketing layer 21 seats againstthe base of an adapter ring 52 and accordingly is properly termed thetoe of the seal, while layer 22 becomes the heel. The adapter may besecured to the face of housing 48' as by stud screws 53. Note that ineither mounting arrangement, lip structure 15 faces the interior of thehousing since this is in its most effective sealing position.

It will be quite apparent from the foregoing that the disposition oflayers 21 and 22 with respect to ring renders the same equally effectivein sealing and anchoring the sealing member in the housing irrespectiveof which layer is used as the leading toe edge of the casing. Likewise,outer rim 13 of the reinforcing ring is equally as effective inanchoring the seal in its installed position. Moreover, once installed,all portions of ring 10 are protected by the resilient coveringmaterial. In this connection, it will be recalled that while thedrawings do not show any appreciable layer of rubber on areas 54 of rim12, a thin flash layer is nevertheless present. To either side of theseareas are the thick radial ribs 55 of rubber formed as the distributionpassages 33 of the mold spider fill with rubber during the moldingoperation.

From the foregoing, it will be appreciated that a simple, versatile andhighly efiicient shaft seal can be made in accordance with the foregoingteachings employing merely a metal core ring embedded in syntheticelastomeric except for a narrow exposed band of material at its outerperiphery. This band of material is bordered by two heavy layers ofelastomeric, either of which can be employed as the toe or as the heelof the seal rim. In either case, the exposed band of metal forms apositive anchorage for locking the seal within its housing whileresilient layers to either side provide a shrink-proof fluid-tightgasketing and supplement the action of the metal-to-metal contact inanchoring the seal in its mounting.

It will also be appreciated that the invention provides a simple andmore economical method of simultaneously sizing, deflashing andfinishing the mounting periphery of a shaft seal.

While only a restricted number of embodiments of the invention have beenspecifically disclosed hereinabove, various alternate constructions willbe readily recognized by those skilled in the art to which the inventionrelates as coming within the principles set forth above.

I claim:

1. That method of making a shaft seal having a rigid cupped ringembedded in resilient synthetic rubber material which comprises, coatingsaid cupped ring with a bonding agent, holding said ring positionedcentrally within a mold cavity and supporting it against downward axialdisplacement by closely-spaced, low-height, widearea bosses in directcontact with one face of said cupped ring and by a ring of axiallydisposed ridges, said ridges being disposed to support said cupped ringfrom closelyspaced points about its inner sidewall, and causingsynthetic rubber stock to flow under high pressure to all parts of themold cavity from a source on the side thereof remote from saidsupporting bosses and ridges, said mold cavity including an annularsealing lip portion concentrio with said cupped ring.

2. That method of making a shaft seal having a rigid cupped ring ofcontinuous circular periphery embedded in resilient synthetic rubbermaterial which comprises; coating said cupper ring with a bonding agent,supporting said ring between the axially spaced walls of a mold cavityby closely-spaced, low-height, wide area mold bosses in direct contactwith one botto'm face of said cupped ring, supporting said ring betweenthe spaced walls of said mold cavity by a ring of axially disposedridges in contact with a side wall of said cupped ring, and causingsynthetic rubber stock to flow under high pressure to all parts of themold cavity from a source on the opposite axial side of said ring fromthe side that is in contact with said bosses, said mold cavity includingan annular sealing lip portion concentric with said cupped ring.

3. That method of making a shaft seal having a rigid cupped ringembedded in resilient elastomeric material which comprises; coating saidcupped ring with a bonding agent, supporting the ring between theaxially spaced walls of a mold cavity by closely-spaced, low-height,Wide-area bosses in direct contact with one bottom face of said ring,supporting said ring between the radially spaced Walls of said cavity bya plurality of rigid ridges circumferentially disposed about and incontact with a side wall of said ring, causing uncured elastomeric stockto flow under high pressure to all parts of the mold cavity from asource on the opposite side of said ring from said bosses, said moldcavity including an annular sealing lip portion concentric with saidcupped ring, subjecting said elastomeric material to heat and pressureto cure the same, and finishing the seal so formed to a predeterminedexterior diameter after removal from said mold cavity by abrading away athin surface layer from the outer side Wall thereof to expose aperipheral edge of said ring.

4. That method of making a shaft seal having a rigid cupped ringprovided with a narrow radially disposed flange at its rim which ring isembedded in resilient elastomeric material comprising; applying abonding agent to said rigid ring, supporting said ring between theopposed radially and axially disposed walls of a mold cavity by means ofclosely-spaced, low-height, wide-area bosses in direct contact with onebottom face of said ring and by means of annularl-y disposed ridges incontact with the inner side Wall of said ring, filling said cavity withuncured elastomeric material under pressure from the side of said ringopposite to the face in contact with said bosses, to embed said ringtherein While the same is supported out of contact with the walls ofsaid cavity, said mold cavity including an annular sealing lip portionconcentric with the side wall of said rigid ring, curing saidelastomeric material under heat and pressure, removing the seal fromsaid cavity, and finishing the outer circumferential surface of saidseal to a predetermined diameter by grinding away a thin layer of curedelastomer as well as of metal from the rim of the radial flange of saidrigid ring, thereby providing a shaft seal having a reinforcing ringembedded therein with -a smooth rim exposed between layers of elastomeron the exterior cylindrical side wall thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,592,326 Bastian July 13, 1926 2,532,080 Benbow NOV. 28, 1950 2,605,199Hawkinson July 29, 1952 2,697,623 Mosher Dec. 21, 1954 2,771,156 Kastenet al Nov. 20, 1956

